Up until the middle of the twentieth century, agriculture all over Europe was low intensity and mainly small scale. Farms differed in land use intensity, seeding and harvesting models, available technology and so on. This in turn lead to much variation in soil fertility and acidity, for example, creating optimal conditions for many different species. Moreover, the “left overs” (hedgerows, ditch sides etc.) between the small fields were highly connected and played an important role in the life cycle of a large variety of organisms. Such agricultural landscapes were (and are) very species rich.

In 1957, the forerunner of today’s European Union, the European Economic Community, adopted the Common Agricultural Policy to increase and secure food production, stabilise food markets and protect the incomes and welfare of farmers. This launched a wave of systematic intensification of agricultural practices: fewer farmers and bigger farms, watercourse rectification, more specialised farming, and the elimination of these “left-overs” (or “small scale linear landscape elements”, in conservation parlance). Such simplification of the landscape meant that across Europe farmland started to look all the same, with a corresponding decrease in biodiversity. Intensive agriculture is not only the major driver of biodiversity loss, but also (together with forestry and other land use) responsible for just under a quarter of global emissions. (1)

In the large-scale intensive agricultural systems of today in western and central Europe, the US, and many other parts of the world, certain types of species are actually stimulated, such as fast-growing grasses, or insects that are adapted to eutrophic conditions. We still see birds, we still see green grass. But many species of native birds, butterflies, plants and bees cannot survive on intensively farmed land. Simply put, the loss of vast areas of semi-natural habitats has resulted in the collapse of numerous plant and animal species.

Here in Europe, the lowlands that are more easily farmed have been so heavily fertilised that even in the permanent grasslands only a few specialised species can survive. Typically, these are fast-growing and very common grass species that use the added nutrients in a highly efficient way to overgrow all other species. This set of maps (from the European Commission’s in-house science service, the Joint Research Centre) shows the nutrient excess of topsoil across a number of European countries.

Of particular note are the excess levels of phosphorus, a consequence of the over-use of fertiliser in intensively farmed land. The levels are certainly extreme in Benelux, southern England, northern France and northern Germany. And along with Hungary and Czechia, these are areas where much biodiversity restoration work is now taking place.

Steps towards restoration

According to the findings of a study carried out in 2016 for the European Commission (2), public authorities and civil society organisations together account for more than two thirds of those engaged in biodiversity restoration work. And although most restoration work is taking place outside Natura 2000 sites, increasing the size of this network of protected areas in the EU (which often includes both farmland and nature reserves) is necessary to ensure the survival of native species and habitats. Restoring biodiversity and nature on former agricultural land can also provide much-needed carbon sinks (for example in wetlands and grasslands) and other ecosystem services, thus mitigating against climate change.

Restoration on farmland involves addressing a number of abiotic conditions (such as hydrology, water quality, correct nutrient level) that nature needs to thrive. For soil restoration, the phosphate level is nowadays the most problematic nutrient to tackle. There can be very heavy nitrate addition, but eventually it will be converted into nitrogen gas and go into the atmosphere. But with phosphate, once it is bound in the soil, it is bound for a very long time – in many cases up to hundreds of years. Unfortunately, plants don’t actually take up a lot of phosphate (about 10-20 times less than nitrogen), and only a small fraction of the pool is removed with the crop. If land has been over-fertilised with phosphate, it will stay that way for a long time.

In the 1970s and 1980s, when biodiversity restoration really began in earnest, traditional methods that had been used by farmers for centuries were used to reconstruct the original nutrient-poor conditions of heathland and grassland areas. One of these methods is sod cutting, which involves taking away the top layer of soil with most plant roots and nutrients without further affecting the soil profile.

For soil restoration, the phosphate level is nowadays the most problematic nutrient to tackle.

But when analysis of the soil profile shows the presence of nutrient excess at a deeper level, more radical measures are necessary. These include topsoil removal and excavation, which typically involves removing the first 15-20 cm of soil. Even up to 50 cm is feasible over a small area. In the Netherlands, excavation projects number in the low hundreds and usually take place on sites ranging from a few to several tens of hectares. This approach has been proven to be very effective in restoring fully functional heathlands within a decade.

Immediately after topsoil removal, the whole soil profile is destroyed and the soil is made almost sterile. About one per cent of the soil ecological community remains; the rest is simply gone. On a large scale, this practice is also very disruptive.

Topsoil removal was the leading technique used by the project LIFE Dwingelderveld, Europe’s largest wet moorland area situated in the Netherlands. Topsoil was removed on 166 hectares of farmland – one of the largest scale excavation projects for biodiversity restoration to date. Over 600 000 m3 of topsoil was excavated during the project, at a cost of around 9000 euros per hectare. It took over four years, with a lot of traffic disruption and noise disturbance in the area (though the excavated soil was used to create sound barriers against a nearby motorway, making the area now very quiet).

Another important factor for the rural population was that farmers and landowners couldn’t make any profit on their land anymore after topsoil removal.

Another way

Around 2005, researchers at the Louis Bolk Institute (located close to Utrecht in the Netherlands), came up with a new, less invasive technique for getting the phosphate out of the soil. This technique, known as p-mining or phytoextraction, was developed with the aim of gaining more social acceptance for nature and biodiversity restoration among farmers and local populations. The researchers managed to put it on the political agenda and into conservation frameworks and plans – providing for a socially more acceptable but much slower (decades instead of years) approach to phosphate removal.

P-mining involves fertilising the grass with potassium and nitrogen, and mowing several times a year. The hay is then used by farmers to feed their cattle in the winter. The basic idea is to stimulate plant growth (and therefore increase phosphate uptake and subsequent removal). Currently it is being tested for the first time at field scale on over 200 hectares within the Natura 2000 site Drents-Friese Wold as part of the project LIFE Going up a level.

One of the remarkable aspects of this project is the cooperation between so many different stakeholders: the farmers, the local municipalities and the water board.

At the site, known locally as “Oude Willem”, the leased fields are mainly grass-clover (these were the most popular, particularly with organic farmers) and grasslands for production. Agreements with the farm tenants determine the way in which p-mining is carried out. Based on the results of soil analyses, the project team guides farmers on fertilisation levels for each field. Early indications are that it will take around five to ten years to achieve a reasonably good result in terms of lowering the phosphate level. After ten years of p-mining, the phosphate level will still be much higher than in cases of top soil removal, so heathlands cannot be restored in this way. But more flower-rich grasslands can – and while maintaining involvement with farmers and landowners.

One of the remarkable aspects of this project is the cooperation between so many different stakeholders: the farmers, the local municipalities and the water board. Project partners include the nature conservation organisation Natuurmonumenten, and state forestery management Staatsbosbeheer (both of which began buying up parcels of land in the area as early as the 1960s).

A role to play for the Common Agricultural Policy

Biodiversity restoration means more to local people than business as usual. Of course, there is a really positive economic impact from tourism – the national park at Dwingerveld gets 2.5 million visitors per year, for example (valued at over 25 million euros per year between 2000-2009). Economic benefit is also seen at other Natura 2000 heathland sites, such as the Hoge Kempen national park in Belgium (which receives some 700 000 visitors per year, who spend a total of 191 million euros). But apart from the economic advantages, there is also a sense of real local pride in the reappearance of native species such as the water lobelia plant (lobelia dortmanna) after topsoil removal in the Dwingelderveld.

Every situation requires different site-specific restoration measures – but it is generally true that this type of work must be supported by large-scale public policy and public funding. No farmer today can make a living from heathland.

The project at Oude Willem exemplifies at least two of the nine objectives of the new common agricultural policy (CAP): chiefly, environmental care, and preserving landscapes and biodiversity. It’s clear that previous attempts to “green” the CAP have not yet delivered. This result (or lack thereof) underlines the fact that fine-sounding green rhetoric must be underpinned by real technical knowledge, of the kind that has been gathered by restoration practitioners over the past three decades. Farmers understand this because they work constantly with physical constraints.

Apart from the economic advantages, there is also a sense of real local pride in the reappearance of native species

Modern farmers will not produce high biodiversity meadows, simply because the productivity of such grasslands is far too low. Sites with high biodiversity need to be managed by specialised (nature conservation) organisations.

But farmers can greatly influence the protection and restoration of (still) rather common farmland species by adopting techniques such as unfertilised flower strips, not too-early mowing (to give meadow birds a chance), not draining meadows too excessively, and more. This would create a network of nature-friendly land that would be mostly sufficient to keep our native species alive (3), even in densely-populated Western Europe.

As European policymakers continue to negotiate the post-2020 CAP, they must ensure that the final policy framework can reward farmers for taking care of baseline biodiversity in this way. Specialised conservation organisations, on the other hand, are better adapted to manage (comparatively small) areas with high biodiversity. By recognising and rewarding these different levels of stewardship, the new CAP can support biodiversity restoration work and its many associated benefits (food and wood production, better water quality, carbon sequestration and flood protection, along with other climate mitigation measures). The most vital benefit of all may simply be a revival of our indigenous species.